Dual-Layer-Structured Nickel Hexacyanoferrate/MnO₂ Composite as a High-Energy Supercapacitive Material Based on the Complementarity and Interlayer Concentration Enhancement Effect

A dual-layer composite structure composed of a metal–organic framework structure (NiHCF) with tunable open channels and typical pseudocapacitive manganese dioxide is constructed here as an electrode material for supercapacitors. This type of structure shows enhanced specific capacitance, high energy density, and excellent rate capability and stability. The specific capacitance of the composite electrode is much larger than the sum of each part, and a synergy effect of the dual-layer structure named “interlayer concentration enhancement effect” (ICE effect for short) was proposed to account for this excellent electrochemical performance

Facile Fabrication of Porous Ni_<i>x</i>Co_3–<i>x</i>O₄ Nanosheets with Enhanced Electrochemical Performance As Anode Materials for Li-Ion Batteries

Herein, we report a novel and facile route for the large-scale fabrication of 2D porous Ni_<i>x</i>Co_3–<i>x</i>O₄ nanosheets, which involves the thermal decomposition of Ni_<i>x</i>Co_1–<i>x</i> hydroxide precursor at 450 °C in air for 2 h. The as-prepared 2D porous Ni_<i>x</i>Co_3–<i>x</i>O₄ nanosheets exhibit an enhanced lithium storage capacity and excellent cycling stability (1330 mA h g^–1 at a current density of 100 mA g^–1 after 50 cycles). More importantly, it can render reversible capacity of 844 mA h g^–1, even at a high current density of 500 mA g^–1 after 200 cycles, indicating its potential applications for high power LIBs. Compared to pure Co₃O₄, the reduction of Co in Ni_<i>x</i>Co_3–<i>x</i>O₄ is of more significance because of the high cost and toxicity of Co. The improved electrochemical performance is attributed to the 2D structure and large amounts of mesopores within the nanosheets, which can effectively improve structural stability, reduce the diffusion length for lithium ions and electrons, and buffer volume expansion during the Li⁺ insertion/extraction processes

Low-Cost, Acid/Alkaline-Resistant, and Fluorine-Free Superhydrophobic Fabric Coating from Onionlike Carbon Microspheres Converted from Waste Polyethylene Terephthalate

Onionlike carbon microspheres composed of many nanoflakes have been prepared by pyrolyzing waste polyethylene terephthalate in supercritical carbon dioxide at 650 °C for 3 h followed by subsequent vacuum annealing at 1500 °C for 0.5 h. The obtained onionlike carbon microspheres have very high surface roughness and exhibit unique hydrophobic properties. Considering their structural similarities with a lotus leaf, we further developed a low-cost, acid/alkaline-resistant, and fluorine-free superhydrophobic coating strategy on fabrics by employing the onionlike carbon microspheres and polydimethylsiloxane as raw materials. This provides a novel technique to convert waste polyethylene terephthalate to valuable carbon materials. At the same time, we demonstrate a novel application direction of carbon materials by taking advantage of their unique structural properties. The combination of recycling waste solid materials as carbon feedstock for valuable carbon material production, with the generation of highly value-added products such as superhydrophobic fabrics, may provide a feasible solution for sustainable solid waste treatment

Nanoporous PtFe Nanoparticles Supported on N‑Doped Porous Carbon Sheets Derived from Metal–Organic Frameworks as Highly Efficient and Durable Oxygen Reduction Reaction Catalysts

Designing and exploring catalysts with high activity and stability for oxygen reduction reaction (ORR) at the cathode in acidic environments is imperative for the industrialization of proton exchange membrane fuel cells (PEMFCs). Theoretical calculations and experiments have demonstrated that alloying Pt with a transition metal can not only cut down the usage of scarce Pt metal but also improve performance of mass activity compared with pure Pt. Herein, we exhibit the preparation of nanoporous PtFe nanoparticles (np-PtFe NPs) supported on N-doped porous carbon sheets (NPCS) via facile in situ thermolysis of a Pt-modified Fe-based metal–organic framework (MOF). The np-PtFe/NPCS exhibit a more positive half-wave potential (0.92 V) compared with commercial Pt/C catalyst (0.883 V). The nanoporous structure allows our catalyst to possess high mass activity, which is found to be 0.533 A·mg_Pt^–1 and 3.04 times better than that of Pt/C (0.175 A·mg_Pt^–1). Moreover, the conversion of PtFe NPs from porous to hollow structure can maintain the activity of electrocatalyst. Our strategy provides a facile design and synthesis process of noble–transition metal alloy electrocatalysts via noble metal modified MOFs as precursors

Experimental and Theoretical Studies on the Effects of Magnetic Fields on the Arrangement of Surface Spins and the Catalytic Activity of Pd Nanoparticles

Nanocatalysts have very high catalytic activities due to surface atoms with their unpaired spins. It is the purpose of this paper to investigate the effect of magnetic fields (MFs) on the arrangement of surface spins and their catalytic activities. Pd nanoparticles supported on MIL-100­(Cr) were selected as catalysts for the reduction of 4-nitrophenol under MFs. The result demonstrates that MFs can reduce the reaction time from 2.6 to 1.4 min under 0.5 T. This study first shows that the configuration of surface spins has an effect on the catalytic activity, which can be regulated by a foreign MF

One for Two: Conversion of Waste Chicken Feathers to Carbon Microspheres and (NH₄)HCO₃

Pyrolysis of 1 g of waste chicken feathers (quills and barbs) in supercritical carbon dioxide (sc-CO₂) system at 600 °C for 3 h leads to the formation of 0.25 g well-shaped carbon microspheres with diameters of 1–5 μm and 0.26 g ammonium bicarbonate ((NH₄)­HCO₃). The products were characterized by powder X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Raman spectroscopic, FT-IR spectrum, X-ray electron spectroscopy (XPS), and N₂ adsorption/desorption measurements. The obtained carbon microspheres displayed great superhydrophobicity as fabric coatings materials, with the water contact angle of up to 165.2 ± 2.5°. The strategy is simple, efficient, does not require any toxic chemicals or catalysts, and generates two valuable materials at the same time. Moreover, other nitrogen-containing materials (such as nylon and amino acids) can also be converted to carbon microspheres and (NH₄)­HCO₃ in the sc-CO₂ system. This provides a simple strategy to extract the nitrogen content from natural and man-made waste materials and generate (NH₄)­HCO₃ as fertilizer

Facile Approach to Prepare Pd Nanoarray Catalysts within Porous Alumina Templates on Macroscopic Scales

The separation and reuse of nanocatalysts remains a major challenge. Herein, we report a novel approach to prepare palladium nanowire array catalysts by reducting PdCl₂ in the pores of anodic aluminum oxide (AAO) templates with backside Al sheets via a hydrothermal process. Suzuki coupling reactions and 4-nitrophenol (4-NP) reduction reactions were employed to study the catalytic activity of the nanocatalysts. The nanocatalysts demonstrated good activity, great thermal stability, easy separation, and excellent reusability in both Suzuki reaction and 4-NP reduction

Enhanced Activity for Hydrogen Evolution Reaction over CoFe Catalysts by Alloying with Small Amount of Pt

The hydrogen evolution reaction highly relied on Pt electrocatalysts, with high activity and stability. In the past few years, a host of efforts have been made in the development of novel platinum nanostructures with a low amount of Pt because the scarcity and high price of Pt hinder its practical applications. Here, we report the preparation of PtCo­Fe@CN electrocatalysts with a remarkably reduced Pt loading amount of 4.60% by annealing Pt-doped metal–organic frameworks (MOFs). The electrocatalyst demonstrated an outstanding performance with only 45 mV overpotential to achieve the 10 mA cm^–2 current density, which is quite close to that of the commercial 20% Pt/C catalyst. The enhanced catalytic capability is originated from the modification of the electronic structures of CoFe by alloying with Pt. The results indicate that robust and superstable alloy electrocatalysts which contain a very small amount of noble metal could be prepared by annealing noble metal-doped MOFs

Synthesis of Novel Two-Phase Co@SiO₂ Nanorattles with High Catalytic Activity

Noble metal nanocatalysts with remarkable catalytic properties have attracted much attention; however, the high cost of these materials limits their industrial applications. Here, we design and prepare Co@SiO₂ nanorattles as a mixture of hcp-Co and fcc-Co phases as a substitute. The nanorattles exhibit both superior catalytic activity and high stability for the reduction of <i>p</i>-nitrophenol. The reduction rate nearly follows pseudo-first-order kinetics, and the reaction rate constant is as high as 0.815 min^–1 and is maintained at 0.565 min^–1 even after storing for one month, which is higher than that reported for noble metal nanocatalysts. Such an excellent property can be attributed to the novel two-phase composition and rattle-type structure

Conversion of Chicken Feather Waste to N‑Doped Carbon Nanotubes for the Catalytic Reduction of 4‑Nitrophenol

Poultry feather is renewable, inexpensive and abundantly available. It holds great business potentials if poultry feather can be converted into valuable functional materials. Herein, we describe a strategy for the catalytic conversion of chicken feather waste to Ni₃S₂-carbon coaxial nanofibers (Ni₃S₂@C) which can be further converted to nitrogen doped carbon nanotubes (N-CNTs). Both Ni₃S₂@C and N-CNTs exhibit high catalytic activity and good reusability in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH₄ with a first-order rate constant (<i>k)</i> of 0.9 × 10^–3 s^–1 and 2.1 × 10^–3 s^–1, respectively. The catalytic activity of N-CNTs is better than that of N-doped graphene and comparable to commonly used noble metal catalysts. The N content in N-CNTs reaches as high as 6.43%, which is responsible for the excellent catalytic performance. This strategy provides an efficient and low-cost method for the comprehensive utilization of chicken feathers. Moreover, this study provides a new direction for the application of N-CNTs